Effects of various light curing methods on the leachability of uncured substances and hardness of a composite resin

Abstract

The purpose of this study was to evaluate the effect of the various light curing units (plasma arc, halogen and light-emitting diodes) and irradiation methods (one-step, two-step and pulse) using different light energy densities on the leachability of unreacted monomers (Bis-GMA and UDMA) and the surface hardness of a composite resin (Z250, 3M). Leachability of the specimens immersed for 7 days in ethanol was analysed by HPLC. Vicker's hardness number (VHN) was measured immediately after curing (IC) and after immersion in ethanol for 7 days. Various irradiation methods with three curing units resulted in differences in the amount of leached monomers and VHN of IC when light energy density was lower than 17.0 J cm(-2) (P = 0.05). However, regardless of curing units and irradiation methods, these results were not different when the time or light energy density increased. When similar light energy density was irradiated (15.6-17.7 J cm(-2)), the efficiency of irradiation methods was different by the following order: one-step > or = two-step > pulse. These results suggest that the amount of leached monomers and VHN were influenced by forming polymer structure in activation and initiation stages of polymerization process with different light source energies and curing times.

Temperature rise induced by various light curing units through human dentin

“…The main radiant output from a conventional QTH source is infra-red energy, which isabsorbedbyresincompositesandwhichresultsin increased molecular vibration and heat generation. Thus, conventional QTH LCUs require heatabsorbing filters to reduce the passage of infra-red energyfromthelightsourcetothetooth [4][5][6] .However, the LCU's bulb, reflector, and filter degrade over time due to high operating temperatures, and unfiltered infra-red energy can result in heat generation in the pulpchamber 3,[7][8][9][10][11] . Oflate,thelightemittingdiode(LED)technology has been introduced to the dental profession as an alternative to conventional halogen technology.…”

Influence of Prolonged Light-curing Time on the Shear Bonding Strength of Resin to Bleached Enamel

“…Recently, alternative curing units, such as LED and plasma arc (PAC) curing units, have been introduced into the market. 16 These new technologies offer several advantages over QTH units, one of which is reducing curing time, hence, saving chairside time.…”

Curing Quality of Composites as Influenced by the Filler Content, Light Source and Curing Time

“…Metal ZiO2 nanofiller present in FS might decrease light transmittance through the resin increment due to light scattering [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Hence, one may assume that FS requires high irradiance levels to polymerize bottom surfaces similarly to FZ.…”

“…Inadequate polymerization may stimulate the growth of certain caries-related bacteria around restoration margins and cause adverse biological effects in mammalian cells [3]. Moreover, the majority of unreacted components may be released within the first few days and may enter human body via skin, oral and gastrointestinal mucosa, dentine and pulp [4]. The lower the degree of conversion (DC) of a composite resin, the higher its solubility [5].…”